Recording data or other information-bearing signals on magnetic tape has been practiced for many years. Some of the track formats on magnetic tape facilitate a so-called serpentine scanning of the tape such that the logical beginning and end of the magnetic tape are at the same physical end of the tape. In a preferred form of the invention, it is desired to employ serpentine scanning of data tracks while providing a close control of head-to-tape lateral positioning.
Such control of head-to-tape lateral positioning is best achieved by servoing the head position laterally to the tape. It is also desired, particularly in view of possible high error rates in magnetic tape, to provide a reliable set of servo tracks on a magnetic tape. In combination with the last-mentioned desire, it is also desired to control costs by making the head as low cost as possible. Such desire can be achieved using the present invention by placement and selection of servo track areas on the tape.
Most magnetic tape systems employ heads that are capable of scanning a fixed number of data tracks on a tape. Using the number of gaps in the head and the number of tracks on the tape are fixed with respect to each other. It is desired to provide a tape format and head construction that enables varying the number of active gaps in a head while using the same format on the tape. It is also desired to have servo track areas that are amenable to such variation in the number of tracks to be concurrently accessed.
An important aspect of magnetic tape recording is the ever increasing areal data storage density. It is desired to provide servo track areas that tend to minimize reduction of the data storage capacity of a magnetic tape through the introduction of servo position signals into the tape.
It is also desired to provide servo tracks that can be recorded by a tape device in the field, i.e. in situ.